There are a variety of joining or welding processes used for joining/welding workpieces such as to form an interlocking or metallurgical bond between the pieces.
One class of such processes provides a solid state metallurgical bond, i.e., without heating the workpieces to the melting point thereof or adding a brazing filler metal, and includes at least the following well-known processes:
(i) Pulse Magnetic Forming (PMF).
(ii) Explosive Welding (EW).
(iii) Friction Welding (FW).
(iv) Ultrasonic Welding (USW).
(v) Diffusion Welding (DFW).
(vi) Cold Welding (CW).
(vii) Pressure Gas Welding (PGW).
(viii) Forge Welding (FOW).
Pulsed magnetic forming (PMF) is a process in which a metal workpiece or a portion thereof is put into a rapid motion by a pulsed magnetic field which causes the workpiece to deform. One advantage of the PMF process is in that the specific heat in this process is minimal and consequently there is no or very little heating of the workpiece, and the process is referred to herein as “cold welding” or welding”. In addition, this process does not have the disadvantage of leaving tool marks, as is the case in a variety of other techniques.
The PMF process uses a capacitor bank, a forming coil and often a field shaper for creating an intense magnetic field. The very intense magnetic field required for the PMF process is created, by very rapid discharge of electric energy, stored in the bank capacitor, into the forming coil. The resulting eddy currents that are induced in the workpiece yield magnetic repulsion between the workpiece and the forming coil, and since the forming coil is firmly supported in its position, the repulsion causes the workpiece to deform.
As the workpiece surface moves under the influence of the repulsion force, it absorbs energy from the magnetic field. In order to apply most of the available energy to forming and reduce energy losses due to permeation of energy into the workpiece material (which cause energy waste by resistance heating), the forming magnetic pulse is made to be very short. In most PMF applications, the pulses have a duration between about 10 to about 250 μsec (duration of the first wave of the discharging current).
U.S. Pat. No. 5,824,998 assigned to the present assignee discloses a method of joining or welding of at least a portion of a first metal workpiece to at least a portion of one or more second metal workpieces, comprising inducing movement in said portion of the first workpiece by means of a pulsed magnetic force so as to impact said portion of the second workpiece, the movement imparting a kinetic energy on the at least portion of the first workpiece to cause the two at least portions to join or weld to one another.
U.S. Pat. No. 5,442,846 discloses joining of two adjacent segments of steel pipe having an outer diameter of at least 12 inches, by a bridging sleeve, the sleeve being shrunk to both pipe segments by magnetic forming by means of a short contraction pulse.
Explosive Welding (EW) is a solid state welding process whereby a weld is created between two workpieces by means of a high velocity impact of the workpieces as a result of a controlled detonation. The two workpieces are arranged such that there is a space therebetween, and an explosive charge impacts the two workpieces together at one end forming contact thereat, and the point of contact moves at a rapid velocity across the workpieces as a result of the force created by the detonation until they are fully welded.
Friction Welding (FW) is a solid state process whereby a first workpiece is made to rotate and/or translate with respect to a second workpiece while in contact therewith, the friction created generated between the two providing the energy for the bond
Ultrasonic Welding (USW) is a solid state welding process wherein a first workpiece is pressed against a second workpiece at high pressure, and a high frequency vibration is induced at the contact area therebetween providing the energy for the bond.
Diffusion Welding (DFW) is a solid state welding process wherein a first workpiece is pressed against a second workpiece at high pressure and at elevated temperatures, though less than the melting temperature of the workpieces, without substantial deformation or relative motion of the workpieces at the macroscopic scale.
Cold Welding (CW) is a solid state welding process wherein a first workpiece is pressed against a second workpiece at high pressure and at room temperature, with substantial deformation of the workpieces at the weld.
Pressure Gas Welding (PGW) or Hot Pressure Gas Welding is a solid state welding process wherein a first workpiece is pressed against a second workpiece at high pressure and at elevated temperatures, with substantial deformation of the workpieces at the macroscopic scale.
Forge Welding (FOW) or impact welding is a solid state welding process wherein a first workpiece is subjected to high impact blows against a second workpiece while the workpieces are heated to a welding temperature, with substantial deformation of the workpieces at the contact surfaces.